1. Field of the Invention
The present invention relates to an inkjet recording head and an inkjet recording device.
2. Description of the Related Art
Water-based inkjet printers which are currently on the market utilize dye inks or pigment inks generally having a viscosity of around 5 cps, and on the order of 10 cps at most. It is known that the printing performance can be improved by increasing the viscosity of the ink, for reasons such as: preventing the ink from bleeding when the ink lands on a medium, an increase in the optical color density, drying in a short period of time and suppressing of swelling of the medium due to a reduction in the amount of water contained, the large number of degrees of freedom in designing, in total, such high quality inks, and the like.
On the other hand, when ejecting a high viscosity ink, a high-output pressure generating mechanism is needed, which leads to problems such as an increase in cost and the size of the head, and the like. There has conventionally been known a technique of providing a heater separately at an ejector in order to forcibly lower the viscosity of the ink at the time of ejecting the ink (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2003-220702, FIG. 1 and pages 4 through 6). However, the aforementioned method of heating the ink has the fundamental problem of accelerating deterioration of the ink and damage to the flow path. Further, the inks that can be used therewith are limited to those which do not deteriorate due to heat.
There has also been disclosed a technique in which flowing of the ink in the reverse direction at the time when the ink is ejected is suppressed by a beam-shaped valve, and inks of higher viscosities are ejected (see, for example, JP-A No. 9-327918, FIG. 1 and pages 8 through 9).
The following are disclosed as methods of increasing the power of the pressure generating mechanism itself by utilizing buckling bending by which large deformation can be obtained: a technique using a diaphragm-shaped actuator which deforms due to the difference in the thermal expansions of the actuator and a heat generating body layer (see, for example, JP-A No. 2003-118114, FIG. 3 and pages 4 through 5), and a technique utilizing a cantilevered, beam-shaped actuator of a similar structure (see, for example, JP-A No. 2004-34710, FIG. 13 and pages 6 through 8).
For example, in an inkjet recording head 100 shown in FIGS. 8A and 8B, by deforming an actuator 102 as from FIG. 8A to FIG. 8B, pressure is suddenly applied to ink 101 within an ink chamber 106, and the ink 101 is ejected as an ink drop 108 from a nozzle 104.
However, even in the above-described conventional techniques, it is very difficult to stably eject, at ordinary temperature, high viscosity inks of 50 to 100 cps which greatly exceed a viscosity of 10 cps.